As a combination of a container and a closure for foods, drinks, etc. which has pilferproof characteristics, Japanese Laid-Open Patent Publications Nos. 74445/1981 and 30949/1983 disclose a combination of a container equipped with a mouth-neck portion having formed on its periphery an external thread and an annular anchoring flange positioned beneath the external thread with a closure of a unique shape adapted to be mounted on the mouth-neck portion of the container. The closure has a top panel wall and a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall. A circumferentially extending breakable line is formed on the skirt wall to divide it into a main portion above the breakable line and a pilferproof skirt portion below it. On the inner circumferential surface of the main portion is formed an internal thread adapted for screwable engagement with the external thread formed on the mouth-neck portion. A plurality of anchoring flaps each extending radially inwardly from its one side edge connected to the inner circumferential surface of the pilferproof skirt portion are formed on the inner circumferential surface of the pilferproof skirt portion in circumferentially spaced-apart relationship. In mounting the closure on the mouth-neck portion, the anchoring flaps elastically bend radially outwardly and thereby pass over the annular anchoring flange. When the closure is fully mounted on the mouth-neck portion, the anchoring flaps which have passed over the annular anchoring flange elastically return to their original state and their upper edges engage the under surface of the annular anchoring flange to thereby hamper the axially upward movement of the pilferproof skirt portion.
The aforesaid container-closure combination has various advantages over combinations of containers and closures having other types of pilferproof characteristics, as can also be understood from the disclosures, etc. of the above-cited Japanese Laid-Open Patent Publication No. 74445/1981. However, the present inventor's experiments have revealed the following problem. In the aforesaid container-closure combination, some gap necessarily exists between the inner circumferential surface of the pilferproof skirt portion of the closure and the peripheral surface of the mouth-neck portion of the container when the closure has been mounted in position on the mouth-neck portion of the container. The present inventor turned his attention to this gap, and advanced a thin elongated metallic strip between the inner circumferential surface of the pilferproof skirt portion and the peripheral surface of the mouth-neck portion through this gap so that the thin metallic strip lay along the entire circumference. It was consequently found that the thin metallic strip acted on the anchoring flaps formed on the inner circumferential surface of the pilferproof skirt portion to elastically bend them radially outwardly and thereby reduce greatly the engagement of the anchoring flaps with the under surface of the annular anchoring flange; and therefore by simply turning the closure in the opening direction, the entire closure could be removed from the mouth-neck portion to open the mouth-neck portion without involving breakage of the breakable line, and thus the pilferproof characteristics could be destroyed.